An alternative ‘community’ energy store

[Oldgreybeard]

Yeah, it is a storage heater that plumbs into your central heating…

I remember these from the 1970s, a friend's new build house had a heating system that used a large storage heater that ran internally at several hundred degrees. Like many new builds from that time it was all-electric, using what was then "white meter" rates to charge up the heating and hot water overnight. I can't remember who made it, but do recall that it was very reliable, despite the high temperature that the core worked at. There wasn't much to go wrong, really, it was just an insulated box filled with some sort of iron bricks, a heating element and some simple electromechanical controls. I think the main downside was the same as storage heaters, it drew a heck of a lot of power when heating overnight. I think it ran off three phase, but can't be sure.

[Stinsy]

Yeah, it is a storage heater that plumbs into your central heating…

I remember these from the 1970s, a friend's new build house had a heating system that used a large storage heater that ran internally at several hundred degrees. Like many new builds from that time it was all-electric, using what was then "white meter" rates to charge up the heating and hot water overnight. I can't remember who made it, but do recall that it was very reliable, despite the high temperature that the core worked at. There wasn't much to go wrong, really, it was just an insulated box filled with some sort of iron bricks, a heating element and some simple electromechanical controls. I think the main downside was the same as storage heaters, it drew a heck of a lot of power when heating overnight. I think it ran off three phase, but can't be sure.

It'd be unusual for the house to be 3-phase. Even "all electric" resistively-heated homes were never 3-phase. It was probably 30A.

The problem with all this was the 24/7/365 coal power stations being decommissioned and replaced with ultra-flexible gas. You were lucky to get ecconomy7 off-peak for half the price of peak which was a huge social injustice because it meant the poorest with their storage heaters were paying a fortune to heat their homes.

Luckily for us lot the tide has turned and a grid with a significant proportion of wind will always have super-cheap off-peak electric.

[Bugtownboy]

I know there’s very little detail, but conceptually it could be an attractive alternative to a HP for existing homes.

Decarbonising domestic energy is, I think, only going to work with a mix of solutions to suit the mix of existing housing.

[Oldgreybeard]

It'd be unusual for the house to be 3-phase. Even "all electric" resistively-heated homes were never 3-phase. It was probably 30A.

The problem with all this was the 24/7/365 coal power stations being decommissioned and replaced with ultra-flexible gas. You were lucky to get ecconomy7 off-peak for half the price of peak which was a huge social injustice because it meant the poorest with their storage heaters were paying a fortune to heat their homes.

Luckily for us lot the tide has turned and a grid with a significant proportion of wind will always have super-cheap off-peak electric.

No, they are definitely three phase, no question about it at all. I've just found the details of these old GEC Nightstor units, they draw 19.2kW when charging and 9.6kW when boosting. I was wrong about the temperature they work at, they really work at up to 1,000°C, believe it or not. There is still a company supplying spares for them, as there are some still in use after 50 years. I think they were one of the things that came about from the supposed 1960s belief that nuclear power would give us all electricity that was "too cheap to meter". That worked out well, didn't it?

Edited to add:

Here's some photos of the Nightstor units on this website from a company that keeps them going: http://northernelectricheating.co.uk/ni ... ilers.html

[nowty]

Here's some photos of the Nightstor units on this website from a company that keeps them going: http://northernelectricheating.co.uk/ni ... ilers.html

I bet if you could see the inside of the ZEB it would look very similar to the old Nightstor. I note the video mentioned an air fed heat exchanger which looks like what the Nightstor had / has.


EDIT - I also note that Nowty Towers already has about the same 40kWh of heat + hot water storage as the quoted 40kWh capacity of the ZEB.

[nowty]

An old Nightstor for sale here too if you can cope with the backache of dismantling it and moving it.
https://www.ebay.co.uk/itm/164965960470 ... SwCHhg9GgW

[Mart]

Can I just say, having missed this thread when it started - the reason they use air not water is for simplicity. Even if some air leaks it won't matter, whereas if water leaks it could affect the system. Also, the idea is that a system can be built almost anywhere using local 'dirt' and local steel fabricators. The company provides the clever air to air 'stuff'.

Saw an interview with the team, possibly a year or so back, some great points about simplicity. Once insulation is large enough (I forget the size, possibly 1m) then you don't need more regardless of the size of the hole. It could work with existing holes, such as quarries if they are close enough to a town. Stores could be topped over and then build something, playing fields, solar farm, greenhouse etc etc..

Whilst it's called a sand battery, I think there is flexibility over the chosen material, so long as it's not too large. This goes back to something Donald Sadoway once said about batteries "If you want to make something dirt cheap, make it out of dirt–preferably dirt that is locally sourced."

[Oldgreybeard]

Here's some photos of the Nightstor units on this website from a company that keeps them going: http://northernelectricheating.co.uk/ni ... ilers.html

I bet if you could see the inside of the ZEB it would look very similar to the old Nightstor. I note the video mentioned an air fed heat exchanger which looks like what the Nightstor had / has.


EDIT - I also note that Nowty Towers already has about the same 40kWh of heat + hot water storage as the quoted 40kWh capacity of the ZEB.

I think you're almost certainly right. Any patents that GEC may have held will have long since expired and with at least two companies still producing all the parts needed to maintain these things I suspect that the ZEB is really just a slightly re-engineered version of the under-counter version of the Nightstor. They may have changed the controls over from being electromechanical thermostats and timers to more modern stuff, but as the underlying principle of these things has been proven to last for decades it would seem daft to change that much, if at all.

They may have improved on the insulation a bit, I believe that the original Nightstor units used asbestos insulation to withstand the high internal temperature and this probably makes them expensive to get rid of. Like storage heaters, they need to be dismantled to move, as they weigh over a tonne with all the iron bricks fitted.

[Moxi]

I wonder if the "iron Bricks" were actually magnesite Bricks? I was wondering if the modern unit uses refractory bricks such as Magnesia-Carbon as the heat core ? Most of the modern steel making refractory bricks are easy to get hold of if people are considering their own DIY version of this or any other storage heater ?

Probably best to get the ladle refractory brick rather than the EAF or blast furnace bricks though as the latter are very large and extremely heavy. In the steel industry they used Kaolin wool as an insulation media which was good in service up to around 1100 degrees C but I now know that Kaolin wool fibres arising from the thermal destruction of the wool is a health concern. I wonder if this forms a boundary layer between the core and less heat tolerant components?

Moxi